Continuous vacuum filter

ABSTRACT

A continuous vacuum filter wherein the outlet of a feeding unit discharges a wide stream of a suspension of fibrous particles in a liquid carrier onto the upper stretch of an endless belt-like foraminous screen so that the liquid carrier passes through the interstices of the screen and the fibrous particles accumulate on the upper stretch to form thereon a sheet. The width of such sheet can be varied by two impermeable masks which overlap the marginal portions of the upper stretch and are movable toward and away from each other below the outlet of the feeding unit to thus determine the width of that portion of the upper stretch through which the liquid is free to flow. Such width determines the width of the sheet which is formed on the upper stretch. The length of the masks equals or slightly exceeds the length of the outlet, as considered in the direction of lengthwise movement of the upper stretch.

United States Patent {19] Schuller et al.

[ Feb. 12, 1974 I 1 CONTINUOUS VACUUM FILTER [75] Inventors: Wolfgang Schuller, Wertheim; Karl Veeh, Haslock, both of Germany [22] Filed: Oct. 18, 1971 [21] Appl. No.: 189,850

[30] Foreign Application Priority Data Oct. 17, I970 Germany 2051048 [52] US. Cl. 162/353, 162/366 Primary ExaminerS. Leon Bashore Assistant ExaminerRichard V. Fisher Attorney, Agent, or FirmMichael S. Striker [57] ABSTRACT A continuous vacuum filter wherein the outlet of a feeding unit discharges a wide stream of a suspension of fibrous particles in a liquid carrier onto the upper stretch of an endless belt-like foraminous screen so that the liquid carrier passes through the interstices of the screen and the fibrous particles accumulate on the upper stretch to form thereon a sheet. The width of such sheet can be varied by two impermeable masks which overlap the marginal portions of the upper stretch and are movable toward and away from each other below the outlet of the feeding unit to thus determine the width of that portion of the upper stretch through which the liquid is free to flow. Such width determines the width of the sheet which is formed on the upper stretch. The length of the masks equals or slightly exceeds the length of the outlet, as considered in the direction of lengthwise movement of the upper stretch.

6 Claims, 3 Drawing Figures [51] Int. Cl D2lf l/58, D2lf H52 [58] Field of Search 162/353, 346, 366

[56] References Cited UNITED STATES PATENTS 1,375,517 4/l92l Johnson 162/366 2,395,533 2/1946 Clem 162/366 1,734,929 11/1929 Vedder 162/346 3,563,354 2/197! Nisser et al. 162/353 FOREIGN PATENTS OR APPLICATIONS 233,618 8/1909 Germany 162/366 CONTINUOUS VACUUM FILTER BACKGROUND OF THE INVENTION The present invention relates to apparatus for separating fibrous material from a suspension of such material in a liquid carrier, and more particularly to improvements in apparatus for making sheets of fibrous material by intercepting fibrous material which is suspended in a liquid carrier on a moving screen which permits passage of the liquid. Still more particularly, the invention relates to improvements in apparatus of the type known as continuous vacuum filters.

It is already known to feed a suspension of fibrous material onto a travelling endless band-like sieve or screen which intercepts the fibrous material but permits the liquid carrier to pass therethrough so that the screen accumulates a continuous layer or sheet of separated material. As a rule, the suspension is discharged by the outlet of a header whose width equals the maximum contemplated width of the sheet, and the passage of liquid through the upper stretch of the endless screen, and through a foraminous plate-like support below the upper stretch of such screen, is normally assisted by suction.

The just described vacuum filters operate properly when the desired width of the sheet which is accumulated on the upper stretch of the screen equals the width of the outlet of the header which supplies the suspension of fibrous particles in water or another liquid carrier. If the width of the sheet on the filter is excessive, some material along one or both marginal zones of the sheet of segregated fibrous particles is washed away by water sprays. Such water sprays are discharged by suitable nozzle means in a direction at right angles to the plane of the sheet of fibrous particles. It was found that the narrowing of a sheet of fibrous particles can be carried out with water sprays if the fibrous material is pulp of the type used in the manufacture of paper or the like. However, serious problems arise if the sheet consists of glass fibers or the like. This is due to the fact that the water sprays are likely to extract relatively long fibers from the marginal portions of the sheet so that the resulting narrower sheet exhibits ragged edges. Moreover, the thus separated portions of the sheet cannot be readily reused for the making of suspensions because they tend to flocculate upon introduction into a liquid carrier.

SUMMARY OF THE INVENTION An object of the invention is to provide a novel and improved apparatus for segregation of fibrous particles from suspensions of fibrous particles in a liquid carrier in such a way that the segregated particles can form sheets of desired width without any trimming by water sprays or the like.

Another object of the invention is to provide a continuous vacuum filter for fibrous particles which are suspendedin a liquid carrier with novel means for regulating the width of the sheet which the segregated particles form on a travelling foraminous conveyor.

A further object of the invention is to provide the continuous vacuum filter with novel means for changing the dimensions of the sheet forming zone while the filter is idle or in actual use.

An additional object of the invention is to provide a vacuum filter of the above outlined character which can be used for segregation of a wide variety of fibrous particles from water or another liquid carrier, which can be used for continuous or intermittent formation of sheets of fibrous particles having a width which may vary within a wide range, and which does not exhibit the drawbacks of conventional filters.

The invention is embodied in an apparatus for segregating fibrous particles from a suspension of such particles in a liquid carrier, particularly in a continuous vacuum filter. The apparatus comprises a foraminous conveyor which is preferably an endless belt-like screen of constant width having two parallel longitudinally extending marginal portions and being arranged to travel along a predetermined path, preferably in such a way that the upper stretch of the conveyor travels in a substantially horizontal plane, means for moving the conveyor, suspension feeding means having an outlet overlying a predetermined portion of the path to discharge onto the upper stretch of the conveyor a stream of suspension whereby the liquid carrier passes through the upper stretch and the fibrous particles accumulate on the conveyor to form on the upper stretch a sheet which advances with the conveyor along the path, and means for varying the effective width of the aforementioned predetermined portion of the path for the upper stretch of the conveyor. Such means includes at least one impermeable mask (preferably a strip or panel of relatively thin liquid-impermeable material) which overlaps one marginal portion of the upper stretch of the conveyor and is adjustable transversely of the path to thereby vary the width of that portion of the upper stretch through which the liquid carrier is free to pass and hence the width of the sheet which accumulates on and moves with the upper stretch.

The upper stretch of the conveyor preferably travels above a foraminous plate-like support which is located above at least one suction chamber serving to promote the flow of liquid carrier through the interstices of the conveyor and the perforations or apertures of the support. The mask may be disposed between the outlet of the feeding means and the upper stretch of the conveyor or between such upper stretch and the plate-like support. The means for adjusting the mask with reference to the path for the upper stretch of the conveyor may include one or more threaded screws or the like.

The novel features which are considered as characteristics of the invention are set forth in particular in the appended claims. The improved filtering apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary schematic side elevational view of a continuous vacuum filter which embodies one form of the invention;

FIG. 2 is an enlarged fragmentary transverse vertical sectional view as seen in the direction of arrows from the line IIII of FIG. 1; and

FIG. 3 is a similar fragmentary transverse vertical sectional view of a modified filter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, there is shown a portion of a continuous vacuum filter, and more particularly that portion of a continuous vacuum filter which defines the sheet forming zone. The apparatus comprises a suspension feeding unit or header 1 which serves to supply a wide stream of a suspension of fibrous particles to the sheet forming station or zone above the upper stretch of an endless belt-like foraminous conveyor here shown as a sieve or screen 6. The header 1 is provided with an inlet 2 for admission of a continuous stream of suspension and a wedge-like outlet 3 which distributes the suspension over a predetermined area or zone of the upper stretch of the screen 6. The latter is trained over two rollers or drums 4 (only one shown) at least one of which is driven to move the upper stretch in a direction to the left, as viewed in FIG. 1. The filter further comprises guiding and tensioning rolls 5 which engage the lower stretch of the screen 6. The upper stretch of this screen travels above and is supported from below by a stationary plate-like support 7 of foraminous material which does not interfere with the flow of liquid carrier therethrough. A row of suction chambers 8 below the support 7 serves to promote the flow of liquid carrier through the interstices of the upper stretch of the screen 6 and through the apertures or perforations of the support 7. The manner in which the liquid carrier is widthdrawn from the suction chambers 8 is not shown in FIG. 1. The sheet forming zone is located above that portion of the support 7 which is disposed below the open underside of the outlet 3 of the header 1.

One embodiment of the invention is illustrated in detail in FIG. 2 which shows in section a portion of the outlet 3, the upper stretch of the screen 6, the support 7 and a suction chamber 8 (see the line II-II of FIG. I). The width ofthc sheet of fibrous particles which are intercepted by the upper stretch of the screen 6 can be varied by at least one but preferably two sealing strips or masks 9 which are disposed between the upper stretch ofthe screen 6 and the upper side of the support 7. The masks 9 are impermeable to liquid so that they prevent the deposition of fibrous particles on those portions of the upper stretch of the screen 6 which overlie the masks 9. Thus, the width of the sheet of fibrous material which accumulates on the screen 6 will correspond to the distance between the two masks 9. In order to allow for convenient manual or automatic adjustment in the position of the illustrated mask 9, the latter is connected to the inner end portion of a feed screw 10 which is rotatable in a tapped bore provided in a bracket secured to the suction chamber 8 or to another stationary part of the filter. By rotating the feed screw 10, the operator can move the illustrated mask 9 toward and away from the other mask, i.e., in a direction at right angles to the direction of travel of the screen 6. This renders it possible to rapidly change the width of the sheet which is formed at the upper side of the upper stretch of the screen 6, and such adjustment can be carried out when the filter is idle or when the filter is in actual use. It is clear that, at least in some instances, a single mask 9 will suffice to facilitate necessary adjustments in the width of the sheet of fibrous particles, especially if such single mask is movable through a substantial distance such as corresponds to the difference between the contemplated maximum and minimum widths of sheets which are to be produced in apparatus including the structure of FIG. 2. Each mask 9 preferably consists of relatively thin sheet material which is impermeable to liquids and can stand the corrosive action of the carrier which passes through the interstices of the screen 6, through the apertures of the support 7 and is drawn into the suction chambers 8. In some instances, the suction generating means can be dispensed with, for instance, if the feeding unit 1 receives the suspension at an elevated pressure which insures that the liquid carrier will pass through the screen 6 and support 7 at a desired rate. The length of each mask 9 preferably at least equals or slightly exceeds the length of the sheet forming zone (as considered in the direction of travel of the upper stretch of the screen 6).

The fact that the mask 9 is disposed between the screen 6 and support 7 does not result in clogging of interstices in that portion of the screen which overlaps the mask because the deposition of fibrous particles on the screen takes place only in those regions where the liquid carrier is free to pass through the screen. It is clear that a separate adjusting screw 10 can be provided for each of the two masks 9 or that the two masks can be moved simultaneously but in opposite directions.

FIG. 3 illustrates a portion of a modified continuous vacuum filter wherein two masks 9' (only one shown) are disposed between the open side of the outlet 3 and the upper side of the upper stretch of the screen 6. The illustrated mask 9' has a bent-over outer marginal portion of flange which has a tapped bore for the stem of an adjusting screw 10 rotatably supported by a bracket of the outlet 3. By rotating the screw 10, the operator can move the illustrated mask 9 toward or away from the other mask namely, at right angles to the direction of transport of the screen 6. An advantage of the mask 9' shown in FIG. 3 is that it positively prevents penetration of liquid carrier and/or fibrous particles into the overlapped portion of the respective marginal portion of the upper stretch of the screen 6. Otherwise, the construction and mode of operation of the apparatus embodying the structure of FIG. 3 preferably correspond to those of the apparatus shown in FIG. 1. The length of each mask 9, as considered in the direction of travel of the upper stretch of the screen 6, preferably at least equals or slightly exceeds the length of the sheet forming zone.

An important advantage of the improved continuous vacuum filter is that the width of the sheet of fibrous particles which accumulate on the upper stretch of the screen 6 can be varied at will, within a desired range, and without necessitating even partial dismantling of the filter. Moreover, the sheet which accumulates on the screen 6 is provided with satisfactory edges even if the suspension which is fed into the header 1 via inlet 2 contains glass fibers or an analogous fibrous material. The masks 9 or 9' serve as a means for varying the effective width of that portion of the path for the upper stretch of the screen 6 which is overlapped by the outlet 3 of the feeding unit 1.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desiredrto be protected by Letters Patent is set forth in the appended claims.

1. In an apparatus for separating fibers from a suspension of fibers in a liquid carrier, especially an apparatus for forming a web of such fibers, a combination which includes a movable endless foraminous conveyor element upon which the web is formed, a header provided with an outlet overlying the conveyor element from which outlet the suspension of fibers canbe continuously discharged onto said conveyor element, a suction chamber located beneath said conveyor element, a stationary perforated plate-like support element engaging the bottom of and supporting said conveyor element, said perforated support element being located above and forming the top wall of the suction chamber through the perforations of which the liquid carrier can be drawn by suction created in the suction chamber, and means for varying and controlling the width of the web of fibers that is formed on said endless conveyor element, said means comprising at least one thin strip of sheet material which is impervious along its entire width and is located along and above a marginal edge of said perforated support element and which extends from said marginal edge inwardly across the entire edge of said perforated support element, said means being adjustably movable transversely with respect to the marginal edge of the outlet and the marginal edge of the perforated support element for adjusting simultaneously the width of said outlet and the width of said support element so as to control the flow of the suspension of fibers and the liquid carrier through said outlet and across the foraminous conveyor element at the marginal edge of the web of fibers as the web is being formed.

2. A combination as defined in claim 1, in which the strip of impervious sheet material is located above the endless foraminous conveyor element.

3. A combination as defined in claim 1, in which the strip of impervious sheet material is interposed between the endless foraminous conveyor element and the stationary perforated plate-like support element.

4. A combination as defined in claim 1, in which the apparatus is provided on both marginal edges of the conveyor element with said means for varying and controlling the width of the web of fibers that is being formed.

5. A combination as defined in claim 1, in which the position of the strip of impervious sheet material that conveyor element. 

1. In an apparatus for separating fibers from a suspension of fibers in a liquid carrier, especially an apparatus for forming a web of such fibers, a combination which includes a movable endless foraminous conveyor element upon which the web is formed, a header provided with an outlet overlying the conveyor element from which outlet the suspension of fibers canbe continuously discharged onto said conveyor element, a suction chamber located beneath said conveyor element, a stationary perforated plate-like support element engaging the bottom of and supporting said conveyor element, said perforated support element being locAted above and forming the top wall of the suction chamber through the perforations of which the liquid carrier can be drawn by suction created in the suction chamber, and means for varying and controlling the width of the web of fibers that is formed on said endless conveyor element, said means comprising at least one thin strip of sheet material which is impervious along its entire width and is located along and above a marginal edge of said perforated support element and which extends from said marginal edge inwardly across the entire edge of said perforated support element, said means being adjustably movable transversely with respect to the marginal edge of the outlet and the marginal edge of the perforated support element for adjusting simultaneously the width of said outlet and the width of said support element so as to control the flow of the suspension of fibers and the liquid carrier through said outlet and across the foraminous conveyor element at the marginal edge of the web of fibers as the web is being formed.
 2. A combination as defined in claim 1, in which the strip of impervious sheet material is located above the endless foraminous conveyor element.
 3. A combination as defined in claim 1, in which the strip of impervious sheet material is interposed between the endless foraminous conveyor element and the stationary perforated plate-like support element.
 4. A combination as defined in claim 1, in which the apparatus is provided on both marginal edges of the conveyor element with said means for varying and controlling the width of the web of fibers that is being formed.
 5. A combination as defined in claim 1, in which the position of the strip of impervious sheet material that controls the width of the web that is being formed is fixed by means of a rotatable screw moving in a threaded hole in a bracket fixedly attached to a stationary surface of the apparatus.
 6. A combination as defined in claim 1, wherein the length of said strip at least equals the length of said outlet, as considered in the direction of movement of said conveyor element. 